1. Field of the Invention
This invention relates to a variable, constant flow selector valve, and in particular, relates to a selector valve that is useful in emergency breathing devices.
2. Description of the Prior Art
Emergency respiratory units of the type used in hospitals, ambulances and the like, have typically employed flow control valves in the oxygen line from the pressure regulator of the oxygen cylinder. Commonly, the pressure regulator is set to provide a constant, regulated supply pressure, typically at a set value between about 40 and 90 p.s.i.g. and a manually controlled needle valve and the like is provided to regulate the flow of oxygen to the emergency breathing mask. A flow meter, typically of the rotometer type, is provided in the oxygen supply line to provide a visual indication of the oxygen flow rate to the breathing mask which, typically, is set at a value from 1 to about 15 liters per minute. This equipment is relatively bulky and cumbersome since a rotometer is only operable in a vertical position. The system also demands the complete attention of the operator to adjust the flow rate to a preselected value since the operator must observe the rotometer when setting the flow control valve. Emergency operations in a dimly lit environment can often preclude an accurate setting of the flow rate of the prior devices.
It is, therefore, desirable to provide a variable, constant flow selector valve that is more compact and simple in construction than the previously employed combination of needle valve and rotometer. Additionally, it is desirable to provide a device that can be employed in any position thereby greatly facilitating its use under emergency conditions. It is also desirable to provide such a device with positive detent indication of the preselected constant flow rate, thereby eliminating the need for the visual attention of the operator.